Using a single FHT to decode access-based handoff probes from multiple users

ABSTRACT

A method includes scrambling a Walsh sequence with a random sequence to produce a scrambled Walsh sequence. The method also includes transmitting the scrambled Walsh sequence as an access-based handoff probe.

I. CLAIM OF PRIORITY

This application is a divisional application of U.S. application Ser.No. 12/021,961, filed Jan. 29, 2008, now U.S. Pat. No.8,023,398,entitled “USING A SINGLE FHT TO DECODE ACCESS-BASED HANDOFFPROBES FROM MULTIPLE USERS,” which claims the benefit of U.S.Provisional Application No. 60/887,341, filed Jan. 30, 2007, entitled“METHOD AND APPARATUS FOR USING A ACCESS CHANNEL MAC PROTOCOL.”

II. FIELD

The following description relates generally to wireless communicationsand more particularly to access-based handoff probes.

III. DESCRIPTION OF RELATED ART

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE)systems, and orthogonal frequency division multiple access (OFDMA)systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations throughtransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established though a single-in-single-out,multiple-in-single-out, or a multiple-in-multiple-out (MIMO) system.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, where N_(S)≦min{N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system can provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

A MIMO system supports a time division duplex (TDD) and a frequencydivision duplex (FDD) systems. In a TDD system, the forward and reverselink transmissions are on the same frequency region so that thereciprocity principle allows the estimation of the forward link channelfrom the reverse link channel. This enables the access point to extracttransmit beamforming gain on the forward link when multiple antennas areavailable at the access point.

When a device desires to access a sector covered by one or more basestations, the device transmits an access probe. The access probegenerally includes a terminal specific random sequence. Thus, twoterminals sending access probes in most cases have chosen differentrandom sequences. The receiving access point needs to demodulate theaccess probes with the different random sequences, which increasescomplexity and can create delays when granting access.

IV. SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In accordance with one or more aspects and corresponding disclosurethereof, various aspects are described in connection with using a singleFast Hadamard Transform (FHT) to demodulate access-based handoff probesfrom multiple users.

In a particular embodiment, a method includes scrambling a Walshsequence with a random sequence to produce a scrambled Walsh sequenceand transmitting the scrambled Walsh sequence as an access-based handoffprobe.

In another particular embodiment, a wireless communication apparatusincludes a transmitter and a processor configured to scramble a Walshsequence with a random sequence to produce the scrambled Walsh sequence.The processor is further configured to cause a transmitter to transmitthe scrambled Walsh sequence as an access-based handoff probe.

In another particular embodiment, an apparatus includes means forscrambling a Walsh sequence with a random sequence to produce ascrambled Walsh sequence and means for transmitting the scrambled Walshsequence as an access-based handoff probe.

In another particular embodiment, a non-transitory computer-readablemedium includes instructions that, when executed by a processor, causethe processor to scramble a Walsh sequence with a random sequence toproduce a scrambled Walsh sequence. The instructions further cause theprocessor to cause a transmitter to transmit the scrambled Walshsequence as an access-based handoff probe.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

V. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system in accordance withvarious aspects presented herein.

FIG. 2 illustrates a multiple access wireless communication systemaccording to one or more aspects.

FIG. 3 illustrates a system that utilizes a single FHT to process anaccess-based handoff probe.

FIG. 4 illustrates a system for utilizing a single Fast HadamardTransform for access-based handoff probes.

FIG. 5 illustrates a method for using a single Fast Hadamard Transformfor access-based handoff probes.

FIG. 6 illustrates another method for using a single FHT to GrantAccess.

FIG. 7 illustrates a method for determining a PilotLevel.

FIG. 8 illustrates a method for Determining WalshSequenceID and AccessScramblingID outside Access State.

FIG. 9 illustrates a system that facilitates utilizing a single FHT foraccess probes in accordance with one or more of the disclosed aspects.

FIG. 10 illustrates of a system that facilitates utilizing a single FHTin accordance with various aspects presented herein.

FIG. 11 illustrates an exemplary wireless communication system.

FIG. 12 illustrates a system for using a Fast Hadamard Transform foraccess-based handoff probes.

FIG. 13 illustrates a system for using a single Fast Hadamard Transformfor access-based handoff probes.

VI. DETAILED DESCRIPTION

Various aspects are now described with reference to the drawings. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofone or more aspects. It may be evident, however, that such aspect(s) maybe practiced without these specific details. In other instances,well-known structures and devices are shown in block diagram form inorder to facilitate describing these aspects.

As used in this application, the terms “component”, “module”, “system”,and the like are intended to refer to a computer-related entity, eitherhardware, firmware, a combination of hardware and software, software, orsoftware in execution. For example, a component may be, but is notlimited to being, a process running on a processor, a processor, anobject, an executable, a thread of execution, a program, and/or acomputer. By way of illustration, both an application running on acomputing device and the computing device can be a component. One ormore components can reside within a process and/or thread of executionand a component may be localized on one computer and/or distributedbetween two or more computers. In addition, these components can executefrom various computer readable media having various data structuresstored thereon. The components may communicate by way of local and/orremote processes such as in accordance with a signal having one or moredata packets (e.g., data from one component interacting with anothercomponent in a local system, distributed system, and/or across a networksuch as the Internet with other systems by way of the signal).

Furthermore, various aspects are described herein in connection with awireless terminal. A wireless terminal can also be called a system,subscriber unit, subscriber station, mobile station, mobile, mobiledevice, device remote station, remote terminal, access terminal, userterminal, terminal, wireless communication device, user agent, userdevice, or user equipment (UE). A wireless terminal may be a cellulartelephone, a cordless telephone, a Session Initiation Protocol (SIP)phone, a smart phone, a wireless local loop (WLL) station, a personaldigital assistant (PDA), a laptop, a handheld communication device, ahandheld computing device, a satellite radio, and/or another processingdevice for communicating over a wireless system. Moreover, variousaspects are described herein in connection with a base station. A basestation may be utilized for communicating with wireless terminal(s) andmay also be referred to as an access point, Node B, or some otherterminology.

Various aspects or features will be presented in terms of systems thatmay include a number of devices, components, modules, and the like. Itis to be understood and appreciated that the various systems may includeadditional devices, components, modules, etc. and/or may not include allof the devices, components, modules etc. discussed in connection withthe figures. A combination of these approaches may also be used.

Referring now to FIG. 1, a wireless communication system 100 inaccordance with various aspects presented herein is illustrated. System100 can comprise one or more base stations 102 in one or more sectorsthat receive, transmit, repeat, etc., wireless communication signals toeach other and/or to one or more mobile devices 104. Each base station102 can comprise multiple transmitter chains and receiver chains (e.g.,one for each transmit and receive antenna), each of which can in turncomprise a plurality of components associated with signal transmissionand reception (e.g., processors, modulators, multiplexers, demodulators,demultiplexers, antennas, etc.). Each mobile device 104 can comprise oneor more transmitter chains and receiver chains, such as used for amultiple input multiple output (MIMO) system. Each transmitter andreceiver chain can comprise a plurality of components associated withsignal transmission and reception (e.g., processors, modulators,multiplexers, demodulators, demultiplexers, antennas, etc.), as will beappreciated by one skilled in the art.

When a mobile device 104 desires to gain access to system 100, themobile device 104 transmits, and the access network (e.g., base station102) receives, an Access Probe. The access probe can be used for initialaccess or the access probe can be used for handoff within an Active Set,which is a list of base stations with which the mobile device 104 is incommunication. The access network (e.g., base station 102) can respondto an access probe with an Access Grant, which can be communicated overa Shared Signaling MAC Protocol, for example. The access probe can betransmitted on a CDMA segment, which is a certain part of bandwidth thatis set aside for transmission of CDMA sequences. The CDMA sequences caninclude access probes, CQI transmissions, request transmissions, and soforth.

The disclosed aspects relate to utilizing a Fast Hadamard Transform(FHT) that is common to multiple mobile devices 104. Utilizing a commonFHT can mitigate the complexity associated with conventional systemsthat utilize a different FHT for each terminal. Thus, a terminalspecific random sequence has been commonly utilized and the base stationhad to search for each terminal separately, which consumes systemresources. Through the utilization of a common FHT in accordance withthe disclosed aspects, the complexity involved during access requestsand access grants can be mitigated.

Referring now to FIG. 2, a multiple access wireless communication system200 according to one or more aspects is illustrated. A wirelesscommunication system 200 can include one or more base stations incontact with one or more user devices. Each base station providescoverage for a plurality of sectors. A three-sector base station 202includes multiple antenna groups, one including antennas 204 and 206,another including antennas 208 and 210, and a third including antennas212 and 214. According to the figure, only two antennas are shown foreach antenna group, however, more or fewer antennas may be utilized foreach antenna group. Mobile device 216 is in communication with antennas212 and 214, where antennas 212 and 214 transmit information to mobiledevice 216 over forward link 218 and receive information from mobiledevice 216 over reverse link 220. Forward link (or downlink) refers tothe communication link from the base stations to mobile devices, and thereverse link (or uplink) refers to the communication link from mobiledevices to the base stations. Mobile device 222 is in communication withantennas 204 and 206, where antennas 204 and 206 transmit information tomobile device 222 over forward link 226 and receive information frommobile device 222 over reverse link 224.

Each group of antennas and/or the area in which they are designated tocommunicate may be referred to as a sector of base station 202. In oneor more aspects, antenna groups each are designed to communicate tomobile devices in a sector or the areas covered by base station 202. Abase station may be a fixed station used for communicating with theterminals.

There are two types of access transmissions when a mobile device 216,222 desires to establish communication with a base station 202. Thefirst transmission type is initial access, which is utilized byterminals that desire to gain access to system 200. The secondtransmission type is access-based handoff, which involves mobile devices216, 222 that were connected to a first sector or base station 202 anddesire handoff to another sector or base station. In access-basedhandoff, the mobile device has already communicated with the sector towhich handoff is to occur, thus, that sector, in most cases, has alreadyassigned a MAC ID (Medium Access Control Identification) to the mobiledevice. Thus, when requesting access-based handoff, the mobile devicecan transmit the access probe scrambled with its own MAC ID. Throughutilization of a single FHT for multiple devices as disclosed herein,the identification of the mobile devices (and granting access) by thenetwork can be quicker and can be performed with less complexity.

FIG. 3 illustrates a system 300 that utilizes a single FHT to process anaccess-based handoff probe. When a mobile device desires access to anetwork (e.g., initial access, handoff within an active set), the mobiledevice sends an access probe. The access network can respond with anAccess Grant, if access to that network is allowed. System 300 canfacilitate utilization of a single FHT for access probes transmitted bymultiple devices during access-based handoff.

System 300 includes a base station 302 in wireless communication with amobile device 304. Although a number of mobile devices(s) 304 and basestations(s) 302 can be included in an access network, as will beappreciated, a mobile device 304 that transmits communication datasignals to a single base station 302 is illustrated for purposes ofsimplicity.

As discussed, initial handoff occurs when a mobile device has not beenassigned a MAC ID and chooses a random sequence in order to access anetwork. This random sequence can be chosen from a set of 1,024 randomsequences. These 1,024 random sequences are based on a CDMA segment thathas a dimension of 8 OFDM symbols (time) and 112 subcarriers(frequency), resulting in 1,024 modulation symbols.

For access-based handoff, each mobile device (e.g., MAC ID) is assignedany number of sequences. In one example, a device is assigned one tothree sequences, however, the disclosed aspects are not to be limited toany particular number of assigned sequences. The sequences, such as1,024 sequences, are processed by a Walsh function, resulting in 1,024Walsh sequences. These 1,024 Walsh sequences are scrambled by a FHT.Each of the sequences appears to be a random sequence because it is aWalsh sequence scrambled by a random sequence. Since there can be anynumber of sequences assigned to each user, there might be situationswhen more than one FHT has to be performed in order to accommodate allmobile devices in the network. A different random sequence can beutilized for each FHT.

For example, if there are twenty mobile devices in a network, a singleFHT can be utilized. From the first 1,024 sequences, a first mobiledevice is assigned subsequences 0, 1, and 2. A second mobile device isassigned subsequences 3, 4, and 5. A third mobile device is assignedsubsequences 6, 7, 8, and so forth. It should be understood that theassignment of three sequences to each device in the previous example isfor explanation purposes only and in accordance with the disclosedaspects, any number of sequences can be assigned to each device. In asituation where there are 512 mobile devices, for example, two FHTsmight be utilized if more than one sequence is assigned to any singledevice. If there are 1,000 mobile devices, then three FHTs can beutilized, and so on.

In further detail, the various aspects disclosed herein relate to aWalshSequenceID and an AccessScramblingID. The WalshSequenceID is aninteger in the range 0≦WalshSequenceID<N_(ACMPWalshSequences). TheN_(ACMPWalshSequences) is a constant that denotes the number of Walshsequences in a single FHT. In the case of Ultra Mobile Broadband (UMB),N_(ACMPWalshSequence) is equal to 1,024. The AccessScramblingIDidentifies the sequence that is utilized to scramble the Walsh sequence.Its range is determined by the number of MAC IDs and the number ofsequences per MAC ID. In accordance with an aspect, theAccessScramblingID is an integer between 0 and 15, however, other rangescan be utilized. The WalshSequenceID denotes the index of the Walshsequence (within a single FHT) while the AccessScramblingID denotes theindex of the scrambling sequence itself The quantities WalshSequenceIDand AccessScramblingID have a one-to-one relationship with theAccessSequenceID and the AccessType Fields. The AccessType denotes thetype of handoff (=0 indicates initial access or idle state and =1indicates access-based handoff, or connected state). AccessSequenceIDdenotes the index of the access sequence within the set available to theterminal Thus, for access-based handoff, if the terminal chooses fromone of three sequences, for example, AccessSequenceID takes values from0 to 2.

Determining the WalshSequenceID and AccessScramblingID can depend onwhether an Idle State Protocol is in the Access State. Access probetransmission in the Access State of the Idle State Protocol can beutilized to transition to a Connected State, which can be referred to as“initial access”. Access probe transmission outside the Access State ofthe Idle State Protocol can be utilized for “hard” handoff betweendifferent sectors, either on the same frequency or on differentfrequencies. Access probe transmission outside the Access State of theIdle State Protocol can also be used to transition to a Connected Statefrom a Semi-Connected State and/or to obtain timing and power correctionfor a sector.

In connected stated (AccessType=1), AccessSequenceID takes valuesbetween 0 and PilotLevel−1, depending on the forward link channelquality of the sector. In some cases, AccessSequenceID may also dependon other quantities such as the priority level or the desired QoS of theterminal.

Base station 302 includes an access probe receiver 306 that can beconfigured to accept access probes from devices 304 that desire to gainaccess to the sector served by base station 302. The access probe caninclude a Walsh Sequence, which can be scrambled by the mobile device304 through use of a specified random sequence. The random sequence canbe previously communicated to devices within the sector so that thevarious devices utilize the same random sequence for a particularinterval (e.g., 5 ms). In accordance with some aspects, the WalshSequence comprises 1,024 modulation symbols.

In accordance with some aspects, a first subset of mobile devices in thesector (or that desire to gain access to the sector) use a first randomsequence and a second subset of mobile devices utilize a second randomsequence. The different random sequences might be a function of when thedevices transmitted the access probe and/or based on the number ofdevices that might transmit an access probe at any time since only afinite number of devices can be provided sub-sequences of the scrambledsequence (e.g., first device assigned subsequences 0, 1, and 2 andsecond device assigned subsequences 3, 4, and 5).

Base station 302 can also include a demodulator 308 that can beconfigured to demodulate the Walsh Sequence included in the access probewith a FHT, utilizing the random sequence (or more than one randomsequence depending on a current system 300 configuration). In the casewhere multiple access probes are received at substantially the sametime, demodulator 308 can be configured to demodulate the access probesthrough utilization of a single FHT (e.g., single random sequence).

An access determiner 310 can selectively Grant access to the sector(e.g., base station 302) based on the demodulation as well as otherfactors (e.g., system capacity, signal strength, and so forth). TheAccess Grant can be transmitted over a Shared Signaling MAC Protocol.

System 300 can include memory 312 operatively coupled to base station302. Memory 312 can store information related to identifying a singleFHT or random sequence utilized by devices to transmit an access probe,demodulating an access probe based on one or more known randomsequences, selectively transmitting a Grant Access if access to thesector is approved, and other suitable information related to signalstransmitted and received in a communication network. A processor 314 canbe operatively connected to base station 302 (and/or memory 312) tofacilitate analysis of information related to a single FHT to decodeaccess-based handoff probes from multiple users in a communicationnetwork. Processor 314 can be a processor dedicated to analyzing and/orgenerating information received by base station 302, a processor thatcontrols one or more components of system 300, and/or a processor thatboth analyzes and generates information received by base station 302 andcontrols one or more components of system 300.

Memory 312 can store protocols associated with FHT information, takingaction to control communication between base station 302 and mobiledevice 304, etc., such that system 300 can employ stored protocolsand/or algorithms to achieve improved communications in a wirelessnetwork as described herein. Memory 312 and processor 314 may be locatedinside or outside of base station 302. It should be appreciated that thedata store (e.g., memories) components described herein can be eithervolatile memory or nonvolatile memory, or can include both volatile andnonvolatile memory. By way of example and not limitation, nonvolatilememory can include read only memory (ROM), programmable ROM (PROM),electrically programmable ROM (EPROM), electrically erasable ROM(EEPROM), or flash memory. Volatile memory can include random accessmemory (RAM), which acts as external cache memory. By way of example andnot limitation, RAM is available in many forms such as synchronous RAM(DRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rateSDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), anddirect Rambus RAM (DRRAM). Memory 312 of the disclosed aspects areintended to comprise, without being limited to, these and other suitabletypes of memory.

FIG. 4 illustrates a system 400 for utilizing a single Fast HadamardTransform for access-based handoff probes. System 400 includes one ormore base stations 402 in communication with one or more mobile devices404. From time to time, a mobile device 404 might desire to gain accessto a sector served by a base station 402.

In order to gain access, the mobile device 404 can include an encoder406 that can be configured to scramble a Walsh Sequence with a randomsequence to produce a scrambled sequence. The set of Walsh sequences cancomprise 1,024 modulation symbols. The encoder 406 can be provided withthe random sequence that should be utilized to transmit an access-basedhandoff probe. Utilizing a defined random sequence provides efficiencysince a single FHT can be utilized to decode the sequence.

An allocator 408 can be configured to receive an assignment ofsub-sequences of the scrambled sequence. For example, a first device canbe assigned sub-sequences 0, 1, and 2, a second device assignedsub-sequences 3, 4, and 5, and so forth. In such a manner, at least asub-set of devices utilize a common random sequence, which can bedemodulated by base station 402 through utilization of a single FHT. Oneor more of the assigned sub-sequences are utilized to transmit theaccess-based handoff probe. Thus, there might be situations where afirst set of devices utilize a first random sequence and a second set ofdevices utilizes a second random sequence (e.g., there are moresub-sequences that need to be assigned than sub-sequences available inthe random sequence and, thus, a second random sequence is utilized).

Also included is a communicator 410 that can be configured to send thescrambled sequence as an access-based handoff probe. In response to theaccess-based handoff probe, an Access Grant can be received over aShared Signaling MAC Protocol.

In accordance with some aspects, mobile device 404 can include aPilotLevel Selector (not shown) that can be configured to determine aPilotLevel. The PilotLevel can be utilized when determining values of aWalshSequenceID and/or an Access ScramblingID.

Further, system 400 can include memory 412 operatively coupled to mobiledevice 404. Memory 412 can store information related to a randomsequence, a value of a Walsh Sequence, a value of a Pilot Level, a valueof an AccessScramblingID, transmitting an access-based handoff probe,and other suitable information related to signals transmitted andreceived in a communication network. A processor 424 can be operativelyconnected to mobile device 404 (and/or memory 412) to facilitateanalysis of information related to using a single FHT for access-basedhandoff probes in a communication network. Memory 412 and processor 424can be located inside or outside of mobile device 404. For example,memory 412 may be a memory card that could be inserted into mobiledevice 404 or a RAM located inside of mobile device 404. Processor 424can be a processor dedicated to analyzing and/or generating informationreceived by mobile device 404, a processor that controls one or morecomponents of system 400, and/or a processor that both analyzes andgenerates information received by mobile device 404 and controls one ormore components of system 400.

In view of the exemplary systems shown and described above,methodologies that may be implemented in accordance with the disclosedsubject matter, will be better appreciated with reference to thefollowing flow charts. While, for purposes of simplicity of explanation,the methodologies are shown and described as a series of blocks, it isto be understood and appreciated that the claimed subject matter is notlimited by the number or order of blocks, as some blocks may occur indifferent orders and/or concurrently with other blocks from what isdepicted and described herein. Moreover, not all illustrated blocks maybe required to implement the methodologies described hereinafter. It isto be appreciated that the functionality associated with the blocks maybe implemented by software, hardware, a combination thereof or any othersuitable means (e.g. device, system, process, or component).Additionally, it should be further appreciated that the methodologiesdisclosed hereinafter and throughout this specification are capable ofbeing stored on an article of manufacture to facilitate transporting andtransferring such methodologies to various devices. Those skilled in theart will understand and appreciate that a methodology couldalternatively be represented as a series of interrelated states orevents, such as in a state diagram.

FIG. 5 illustrates a method 500 for using a single Fast HadamardTransform for access-based handoff probes. At 502, an access probe isreceived from a mobile device that desires to be granted access to asector served by a base station. The access probe can include a WalshSequence, which, in accordance to some aspects, can comprise 1,024modulation symbols.

At 504, the Walsh Sequence can be demodulated with a Fast HadamardTransform that comprises a random sequence that is common to at least asubset of mobile devices. Additionally, access probes can be receivedfrom two or more devices at substantially the same time. The two or moreaccess probes can be demodulated utilizing a single FHT. In accordancewith some aspects, a second subset of mobile devices can utilize asecond random sequence. This second random sequence can be utilized todemodulate the Walsh Sequence (e.g., single FHT).

The mobile device that sent the access probe can be selectively grantedaccess to the sector, at 506. This can include transmitting an AccessGrant over a Shared Signaling MAC Protocol.

FIG. 6 illustrates another method 600 for using a single FHT to GrantAccess. Method 600 starts, at 602, when a Walsh Sequence is scrambledwith a random sequence to produce a scrambled sequence. The randomsequence can be utilized by more than one device in order for a singleFHT to be utilized with demodulating the scrambled sequence.

At 604, an assignment of one or more sub-sequences of the scrambledsequence is received. The scrambled sequence can be transmitted, at 606,in the form of an access-based handoff probe. One or more of thesub-sequences can be utilized within the access-based handoff probe. Ifaccess is granted, an Access Grant can be received over a SharedSignaling MAC Protocol.

FIG. 7 illustrates a method 700 for determining a PilotLevel. Thequantity PilotLevel is utilized for the values of WalshSequenceID andAccess Scrambling ID, as discussed above. In order to determine thePilotLevel, both PilotThreshold1 and Pilot Threshold2 are utilized.Method 700 starts, at 702, when the pilot power from the sector to wherean access attempt is being made is ascertained. Various channels can beutilized to determine the received power these channels can includeF-OSICH (Other Sector Interference Indication), F-PBCCH (PacketBroadcast Control Channel), F-PPICH (Preamble Pilot Channel) and/orF-SBCCH (Secondary Broadcast Control Channel). For example, the F-OSICHpilot power is the received power of the F-OSICH (e.g., OFDM symbolswith indices 4 and 5 from a superframe preamble). The determination ofthe pilot power can be based on a measurement or through other means ofgathering the information. At 704, the power of a given sector isascertained (e.g., through measuring the power or obtaining in othermanners).

A superframe is the fundamental unit of transmission on both forward andreverse links. A forward link superframe consists of a superframepreamble followed by N_(FLPHYFrames) FL PHY Frames. A reverse linksuperframe consists of N_(RLPHFrames) RL PHY Frames. In accordance withsome aspects, N_(FLPHYFrames) and N_(RLPHYFrames) can be constants inthe system and N_(FLPHYFrames)=N_(RLPHYFrames)=25. Each superframe canbe uniquely identified by a superframe index that is incremented everysuperframe. The superframe index is related to the system time.Furthermore, each FL PHY Frame and each RL PHY Frame can be uniquelyidentified by an FL PHY Frame index and an RL PHY Frame indexrespectively.

At 706, the ratio of the pilot power from the sector to where an accessattempt is being made and the total power received in the channel timeslot is determined. This ratio can be measured in dB. Based on theratio, a determination is made, at 708, whether the ratio is belowPilotThreshold1. If the determination is that the ratio is belowPilotThreshold1 (“YES”), method 700 continues, at 710, and thePilotLevel is set to 0. If the determination is that the ratio is abovePilotThreshold1 (“NO”), a determination is made, at 712, whether theratio is below PilotThreshold2. If the ratio is above PilotThreshold1and below PilotThreshold2 (“YES”), at 714, the PilotLevel is set to 1.If the ratio is below neither PilotThreshold1 nor PilotThreshold2(“NO”), method 700 continues, at 716, and the PilotLevel is set to 2.

Thus, as discussed above, to determine the PilotLevel, the accessterminal can utilize PilotThreshold1 and PilotThreshold2. The values ofWalshSequenceID and AccessScramblingID utilize, as one parameter, thevalue of the quantity PilotLevel.

FIG. 8 illustrates a method 800 for Determining WalshSequenceID andAccessScramblingID outside Access State. At 802, the AccessType field isset equal to 1. At 804, the AccessSequenceID field is set equal to thePilotLevel. The PilotLevel can be determined in a manner similar to thatdescribed in method 700 of FIG. 7.

The WalshSequenceID and the AccessScramblingID can depend on the MAC IDof the access terminal from the target sector of the access probe. TheWalshSequenceID can be set, at 806, to(MACID*N_(ACMPPilotLevels)+AccessSequenceID) mod N_(ACMPWalshSequences).The AccessScramblingID can be set, at 808, to└(MACID*N_(ACMPPilotLevels)+AccessSequenceID/N_(ACMPWalshSequences)┘+1.

With reference now to FIG. 9, illustrated is a user device 900 thatfacilitates utilizing a single FHT for access probes in accordance withone or more of the disclosed aspects. User device 900 comprises areceiver 902 that can receive a signal from, for example, a receiverantenna. The receiver 902 can perform typical actions thereon, such asfiltering, amplifying, downconverting, etc. the received signal. Thereceiver 902 can also digitize the conditioned signal to obtain samples.A demodulator 904 can obtain received symbols for each symbol period, aswell as provide received symbols to a processor 906.

Processor 906 can be a processor dedicated to analyzing informationreceived by receiver component 902 and/or generating information fortransmission by a transmitter 908. In addition or alternatively,processor 906 can control one or more components of user device 900,analyze information received by receiver 902, generate information fortransmission by transmitter 908, and/or control one or more componentsof user device 900. Processor 906 may include a controller componentcapable of coordinating communications with additional user devices.

User device 900 can additionally comprise memory 908 operatively coupledto processor 906 and that can store information related to coordinatingcommunications and any other suitable information. Memory 910 canadditionally store protocols associated with sample rearrangement. Itwill be appreciated that the data store (e.g., memories) componentsdescribed herein can be either volatile memory or nonvolatile memory, orcan include both volatile and nonvolatile memory. By way ofillustration, and not limitation, nonvolatile memory can include readonly memory (ROM), programmable ROM (PROM), electrically programmableROM (EPROM), electrically erasable ROM (EEPROM), or flash memory.Volatile memory can include random access memory (RAM), which acts asexternal cache memory. By way of illustration and not limitation, RAM isavailable in many forms such as synchronous RAM (SRAM), dynamic RAM(DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM),enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM(DRRAM). The memory 908 of the subject systems and/or methods isintended to comprise, without being limited to, these and any othersuitable types of memory. User device 900 can further comprise a symbolmodulator 912 and a transmitter 908 that transmits the modulated signal.

Receiver 902 is further operatively coupled to an encoder 914 thatscrambles a Walsh Sequence with a random sequence to produce a scrambledsequence. The encoder 914 can be provided with the random sequence sothat a single FHT can be utilized to decode the sequence. Additionally,receiver 902 can be operatively coupled to an allocator 916 that receivean assignment of one or more sub-sequences of the scrambled sequence.The transmitter 908 can send the scrambled sequence as an access-basedhandoff probe. In response to the access probe, receiver 902 can receivean Access Grant, which can be transmitted over a Shared Signaling MACProtocol.

FIG. 10 is an illustration of a system 1000 that facilitates utilizing asingle FHT in accordance with various aspects presented herein. System1000 comprises a base station or access point 1002. As illustrated, basestation 1002 receives signal(s) from one or more user devices 1004 by areceive antenna 1006, and transmits to the one or more user devices 1004through a transmit antenna 1008.

Base station 1002 comprises a receiver 1010 that receives informationfrom receive antenna 1006 and is operatively associated with ademodulator 1012 that demodulates received information. Demodulatedsymbols are analyzed by a processor 1014 that is coupled to a memory1016 that stores information related to broadcast-multicast waveformsembedded in a unicast waveform. A modulator 1018 can multiplex thesignal for transmission by a transmitter 1020 through transmit antenna1008 to user devices 1004.

Processor 1014 is further coupled to an access determiner 1016. Receiver1010 can receive an access probe from one or more mobile devices thatdesire to gain access to a sector served by base station 1002.Demodulator 1012 can demodulate a Walsh Sequence included in the accessprobe utilizing an FHT. Access determiner 1016 can selectively Grant theone or more mobile devices access to the sector.

FIG. 11 illustrates an exemplary wireless communication system 1100.Wireless communication system 1100 depicts one base station and oneterminal for sake of brevity. However, it is to be appreciated thatsystem 1100 can include more than one base station or access pointand/or more than one terminal or user device, wherein additional basestations and/or terminals can be substantially similar or different fromthe exemplary base station and terminal described below. In addition, itis to be appreciated that the base station and/or the terminal canemploy the systems and/or methods described herein to facilitatewireless communication there between.

Referring now to FIG. 11, on a downlink, at access point 1105, atransmit (TX) data processor 1110 receives, formats, codes, interleaves,and modulates (or symbol maps) traffic data and provides modulationsymbols (“data symbols”). A symbol modulator 1115 receives and processesthe data symbols and pilot symbols and provides a stream of symbols. Asymbol modulator 1115 multiplexes data and pilot symbols and obtains aset of N transmit symbols. Each transmit symbol may be a data symbol, apilot symbol, or a signal value of zero. The pilot symbols may be sentcontinuously in each symbol period. The pilot symbols can be frequencydivision multiplexed (FDM), orthogonal frequency division multiplexed(OFDM), time division multiplexed (TDM), frequency division multiplexed(FDM), or code division multiplexed (CDM).

A transmitter unit (TMTR) 1120 receives and converts the stream ofsymbols into one or more analog signals and further conditions (e.g.,amplifies, filters, and frequency upconverts) the analog signals togenerate a downlink signal suitable for transmission over the wirelesschannel. The downlink signal is then transmitted through an antenna 1125to the terminals. At terminal 1130, an antenna 1135 receives thedownlink signal and provides a received signal to a receiver unit (RCVR)1140. Receiver unit 1140 conditions (e.g., filters, amplifies, andfrequency downconverts) the received signal and digitizes theconditioned signal to obtain samples. A symbol demodulator 1145 obtainsN received symbols and provides received pilot symbols to a processor1150 for channel estimation. Symbol demodulator 1145 further receives afrequency response estimate for the downlink from processor 1150,performs data demodulation on the received data symbols to obtain datasymbol estimates (which are estimates of the transmitted data symbols),and provides the data symbol estimates to an RX data processor 1155,which demodulates (i.e., symbol demaps), deinterleaves, and decodes thedata symbol estimates to recover the transmitted traffic data. Theprocessing by symbol demodulator 1145 and RX data processor 1155 iscomplementary to the processing by symbol modulator 1115 and TX dataprocessor 1110, respectively, at access point 1105.

On the uplink, a TX data processor 1160 processes traffic data andprovides data symbols. A symbol modulator 1165 receives and multiplexesthe data symbols with pilot symbols, performs modulation, and provides astream of symbols. A transmitter unit 1170 then receives and processesthe stream of symbols to generate an uplink signal, which is transmittedby the antenna 1135 to the access point 1105.

At access point 1105, the uplink signal from terminal 1130 is receivedby the antenna 1125 and processed by a receiver unit 1175 to obtainsamples. A symbol demodulator 1180 then processes the samples andprovides received pilot symbols and data symbol estimates for theuplink. An RX data processor 1185 processes the data symbol estimates torecover the traffic data transmitted by terminal 1130. A processor 1190performs channel estimation for each active terminal transmitting on theuplink.

Processors 1190 and 1150 direct (e.g., control, coordinate, manage, . .. ) operation at access point 1105 and terminal 1130, respectively.Respective processors 1190 and 1150 can be associated with memory units(not shown) that store program codes and data. Processors 1190 and 1150can also perform computations to derive frequency and impulse responseestimates for the uplink and downlink, respectively.

For a multiple-access system (e.g., FDMA, OFDMA, CDMA, TDMA, and thelike), multiple terminals can transmit concurrently on the uplink. Forsuch a system, the pilot subbands may be shared among differentterminals. The channel estimation techniques may be used in cases wherethe pilot subbands for each terminal span the entire operating band(possibly except for the band edges). Such a pilot subband structurewould be desirable to obtain frequency diversity for each terminal. Thetechniques described herein may be implemented by various means. Forexample, these techniques may be implemented in hardware, software, or acombination thereof For a hardware implementation, the processing unitsused for channel estimation may be implemented within one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,other electronic units designed to perform the functions describedherein, or a combination thereof With software, implementation can bethrough modules (e.g., procedures, functions, and so on) that performthe functions described herein. The software codes may be stored inmemory unit and executed by the processors 1190 and 1150.

It is to be understood that the embodiments described herein may beimplemented by hardware, software, firmware, middleware, microcode, orany combination thereof When the systems and/or methods are implementedin software, firmware, middleware or microcode, program code or codesegments, they may be stored in a machine-readable medium, such as astorage component. A code segment may represent a procedure, a function,a subprogram, a program, a routine, a subroutine, a module, a softwarepackage, a class, or any combination of instructions, data structures,or program statements. A code segment may be coupled to another codesegment or a hardware circuit by passing and/or receiving information,data, arguments, parameters, or memory contents. Information, arguments,parameters, data, etc. may be passed, forwarded, or transmitted usingany suitable means including memory sharing, message passing, tokenpassing, network transmission, etc.

For a software implementation, the techniques described herein may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The software codes may be storedin memory units and executed by processors. The memory unit may beimplemented within the processor or external to the processor, in whichcase it can be communicatively coupled to the processor through variousmeans as is known in the art. Further, at least one processor mayinclude one or more modules operable to perform the functions describedherein.

With reference to FIG. 12, illustrated is a system 1200 for using a FastHadamard Transform for access-based handoff probes. For example, system1200 can reside at least partially within a base station. It is to beappreciated that system 1200 is represented as including functionalblocks, which can be functional blocks that represent functionsimplemented by a processor, software, or combination thereof (e.g.,firmware). System 1200 includes a logical grouping 1202 of electricalcomponents that can act separately or in conjunction. For instance,logical grouping 1202 can include an electrical component for receivingan access probe 1204. The access probe can be received from a mobiledevice, wherein the mobile device requests access to a serving area. Theaccess probe can include a Walsh Sequence. In accordance with someaspects, the Walsh Sequence can include 1,024 modulation systems.

Further, logical grouping 1202 can comprise an electrical component fordemodulating a Walsh Sequence, included in the access probe, with a FastHadamard Transform 1206. The Fast Hadamard Transform (FHT) can comprisea random sequence that is common to one or more devices that maytransmit access probes.

In accordance with some aspects, system 1200 includes an electricalcomponent for selectively granting the mobile device access to thesector based on the demodulation (not shown). Selectively grantingaccess to the sector can include transmitting an Access Grant over aShared Signaling MAC Protocol. Additionally or alternatively, system1200 can include an electrical component for receiving access probesfrom two or more devices at substantially the same time (not shown).Also included can be an electrical component for demodulating the WalshSequences included in the access probes with a Fast Hadamard Transformthat comprises the random sequence.

Additionally, system 1200 can include a memory 1208 that retainsinstructions for executing functions associated with electricalcomponents 1204, 1206, and/or other electrical components. While shownas being external to memory 1208, it is to be understood that one ormore of electrical components 1204, 1206 can exist within memory 1208.

Turning to FIG. 13, illustrated is a system 1300 for using a single FastHadamard Transform for access-based handoff probes. System 1300 canreside within an access terminal, for instance. As depicted, system 1300includes functional blocks that can represent functions implemented by aprocessor, software, or combination thereof (e.g., firmware). System1300 includes a logical grouping 1302 of electrical components that canact separately or in conjunction. Logical grouping 1302 can include anelectrical component for scrambling a Walsh Sequence with a randomsequence to produce a scrambled sequence 1004. The random sequence canbe a sequence that was previously communicated to one or more devices.Moreover, logical grouping 1302 can include an electrical component fortransmitting the scrambled sequence as an access-based handoff probe1306. At least one sub-sequence of the scrambled sequence can beincluded in the handoff probe.

In accordance with some aspects, logical grouping 1302 can include anelectrical component for receiving an Access Grant over a SharedSignaling Mac Protocol (not shown). The Access Grant can be received inresponse to the transmitted access-based handoff probe.

Additionally, system 1300 can include a memory 1308 that retainsinstructions for executing functions associated with electricalcomponents 1304, 1306, and/or other components. While shown as beingexternal to memory 1308, it is to be understood that electricalcomponents 1304, 1306 can exist within memory 1308.

Various aspects or features described herein may be implemented as amethod, apparatus, or article of manufacture using standard programmingand/or engineering techniques. The term “article of manufacture” as usedherein is intended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. For example,computer-readable media can include but are not limited to magneticstorage devices (e.g., hard disk, floppy disk, magnetic strips, etc.),optical disks (e.g., compact disk (CD), digital versatile disk (DVD),etc.), smart cards, and flash memory devices (e.g., EPROM, card, stick,key drive, etc.). Additionally, various storage media described hereincan represent one or more devices and/or other machine-readable mediafor storing information. The term “machine-readable medium” can include,without being limited to, wireless channels and various other mediacapable of storing, containing, and/or carrying instruction(s) and/ordata. Additionally, a computer program product may include a computerreadable medium having one or more instructions or codes operable tocause a computer to perform the functions described herein.

What has been described above includes examples of one or moreembodiments. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the aforementioned embodiments, but one of ordinary skill inthe art may recognize that many further combinations and permutations ofvarious embodiments are possible. Accordingly, the described embodimentsare intended to embrace all such alterations, modifications andvariations that fall within scope of the appended claims. To the extentthat the term “includes” is used in either the detailed description orthe claims, such term is intended to be inclusive in a manner similar tothe term “comprising” as “comprising” is interpreted when employed as atransitional word in a claim. Furthermore, the term “or” as used ineither the detailed description of the claims is meant to be a“non-exclusive or”.

What is claimed is:
 1. A method for using a single Fast HadamardTransform for access-based handoff probes, the method comprising:scrambling, at a first device, a first Walsh sequence with a randomsequence to produce a first scrambled Walsh sequence, the randomsequence to be used by a plurality of devices including the first deviceto scramble Walsh sequences during generation of handoff probes, whereineach of the Walsh sequences is decodable using a single Fast HadamardTransform (FHT) including the random sequence; and transmitting anaccess-based handoff probe that includes at least a portion of the firstscrambled Walsh sequence.
 2. The method of claim 1, further comprisingreceiving an access grant over a shared signaling medium access controlprotocol in response to the transmitted access-based handoff probe. 3.The method of claim 1, further comprising receiving an assignment of oneor more sub-sequences of the first scrambled Walsh sequence at the firstdevice, wherein the portion of the first scrambled Walsh sequenceincluded in the access-based handoff probe corresponds to the one ormore sub-sequences.
 4. The method of claim 1, wherein the firstscrambled Walsh sequence comprises 1,024 modulation symbols.
 5. Themethod of claim 1, further comprising: receiving the random sequence atthe first device.
 6. The method of claim 1, wherein the random sequenceis to be used by the plurality of devices during a particular interval,and wherein a second random sequence is to be used by the plurality ofdevices during a second interval.
 7. The method of claim 6, wherein theparticular interval is 5 milliseconds.
 8. The method of claim 1, whereinthe random sequence is based on a transmission time of the access-basedhandoff probe, a maximum number of devices that can transmitaccess-based handoff probes at a particular time, or a combinationthereof.
 9. The method of claim 1, wherein the random sequence is basedon a pilot level.
 10. A wireless communications apparatus, the apparatuscomprising: a transmitter; and a processor configured to: scramble afirst Walsh sequence with a random sequence to produce a first scrambledWalsh sequence, the random sequence to be used by a plurality of devicesto scramble Walsh sequences during generation of handoff probes, whereineach of the Walsh sequences is decodable using a single Fast HadamardTransform (FHT) including the random sequence; and cause the transmitterto transmit an access-based handoff probe that includes at least aportion of the first scrambled Walsh sequence.
 11. The wirelesscommunications apparatus of claim 10, further comprising a receiverconfigured to: receive the random sequence; and receive an access grantover a shared signaling medium access control protocol in response tothe access-based handoff probe.
 12. The wireless communicationsapparatus of claim 10, further comprising receiving an assignment of oneor more sub-sequences of the first scrambled Walsh sequence, wherein theportion of the first scrambled Walsh sequence included in theaccess-based handoff probe corresponds to the one or more sub-sequences.13. The wireless communications apparatus of claim 10, wherein the firstscrambled Walsh sequence comprises 1,024 modulation symbols.
 14. Thewireless communications apparatus of claim 10, further comprising amemory configured to store information related the first scrambled Walshsequence and the access-based handoff probe.
 15. A wirelesscommunications apparatus that uses a single Fast Hadamard Transform foraccess-based handoff probes, the apparatus comprising: means forscrambling a first Walsh sequence with a random sequence to produce afirst scrambled Walsh sequence, the random sequence to be used by aplurality of devices to scramble Walsh sequences during generation ofhandoff probes, wherein each of the Walsh sequences is decodable using asingle Fast Hadamard Transform (FHT) including the random sequence; andmeans for transmitting an access-based handoff probe that includes atleast a portion of the first scrambled Walsh sequence.
 16. The wirelesscommunications apparatus of claim 15, further comprising: means forreceiving the random sequence; and means for receiving an access grantover a shared signaling medium access control protocol in response tothe transmitted access-based handoff probe.
 17. The wirelesscommunications apparatus of claim 15, further comprising means forreceiving an assignment of one or more sub-sequences of the firstscrambled Walsh sequence, wherein the portion of the first scrambledWalsh sequence included in the access-based handoff probe corresponds tothe one or more sub-sequences.
 18. The wireless communications apparatusof claim 15, wherein the first scrambled Walsh sequence comprises 1,024modulation symbols.
 19. A non-transitory computer-readable mediumcomprising instructions that, when executed by a processor, cause theprocessor to: scramble, at a first device, a first Walsh Sequence with arandom sequence to produce a first scrambled Walsh sequence, the randomsequence to be used by a plurality of devices including the first deviceto scramble Walsh sequences during generation of handoff probes, whereineach of the Walsh sequences is decodable using a single Fast HadamardTransform (FHT) including the random sequence; and cause a transmitterto transmit an access-based handoff probe that includes at least aportion of the first scrambled Walsh sequence.
 20. The non-transitorycomputer-readable medium of claim 19, wherein the instructions furthercause the processor to receive an assignment of one or moresub-sequences of the first scrambled Walsh sequence, wherein the portionof the first scrambled Walsh sequence included in the access-basedhandoff probe corresponds to the one or more sub-sequences.